Air can enter a hydronic (hot water) heating system in number of ways. Most typically, air enters the system as a result of some repair or replacement of a component of the system. If, for example, a boiler is replaced, the entire system typically must be drained and refilled with water.
The removal of air in a hot water heating system is conventionally done in two steps. The first step is to remove the large pockets of air by purging the system with a hose. The second step is to remove the left-over smaller pockets of air by an air scoop or microbubbler.
In the first step, a shut-off valve is opened on the fill line leading to the boiler and the system is filled until 12 psi is reached. Then a hose is attached to a drain valve in the system piping and the shut-off valves for each split off of each zone are closed. The drain valve is opened and the pressure is increased in the system by adjusting the fill valve to let water into the system. If that doesn't work, the fill valve must be bypassed with a double-end hose. Most of the time the drain valves are not properly placed to do this. The water is then circulated through the system until new water replaces the water already in the system. The hose is then moved to the next drain valve and the step of circulating water to replace existing water with new water is repeated for each split of each heating loop. This task takes 1.25-2.5 hours and must be added to every repair done in the system. If the fill valve breaks due to excessive pressures during filling of the system, the entire process may have to be repeated.
In the second step, after the biggest pockets of air are gone, small bubbles remain, causing gurgling noises in the pipes of the hot water system. These small bubbles are removed by air scoops or microbubblers installed in the system. If properly installed, these devices will eventually purge most of the remaining air within 24 hours and the system should circulate smoothly and quietly.
If the smaller bubbles are not removed, they can accumulate into bigger pockets of air. These large pockets of air, if they are drawn through the system to the impeller chamber of the circulator, can cause stalling of circulation of the water through the system, so that no heat is delivered to the radiators located downstream of the circulator. In other cases, the air pocket can become trapped in one of the zones of the heating system, preventing circulation through that zone. If these problems occur in the winter, there is the possibility of the pipes freezing and bursting if the problems are not promptly solved.
A number of systems have been proposed to provide gas separation equipment in a hyrdronic heating system, but to date, none of the proposed systems have been suitable for use in retrofit applications, i.e., installation into preexisting hydronic heating systems. Thus, the system in U.S. Pat. No. 3,290,864 is complicated, and would require expensive repiping to install in a preexisting system due to the non-standard positioning of the pump inlet and outlet; and due to the inability to install the pump where system piping is run close to a wall. The system in U.S. Pat. No. 4,775,292 is not suitable for orientation in more than one direction, thus limiting its application to limited situations where a prexisting circulator pump is oriented in the same way as the intended use of the system shown in this patent. In addition, this system would not be useful to install the pump where system piping runs close to a wall.
It would be desirable to provide a circulator for hydronic systems which can automatically remove air in the system, without need for laborious hose purging of the system, and which is suitable for retrofit applications regardless of the positioning or orientation of the existing circulator or piping in the system.